US7438687B2 - Patient monitoring system with blood pressure measurement capacity - Google Patents

Abstract

A patient monitoring system including a sensing-recording device that attaches to a patient and a probe utilized by attending personnel at a trauma site. After an initial interaction between the probe and the sensing-recording device, the sensing-recording device samples one or more physiological parameters and stores time stamped readings in a first memory. The probe is adapted to take other measurements including pulse data, download the data from the first memory of the sensing-recording device, manipulate the collective data and return data to a second memory in the sensing-recording device. The probe is also adapted to combine data from the sensing-recording device and its pulse data to provide a blood pressure measurement.

Description

FIELD OF THE INVENTION

This invention generally relates to monitoring physiological parameters of a patient and more specifically to the monitoring of such parameters in patients who are geographically remote from a medical facility.

DESCRIPTION OF RELATED ART

Monitoring of a patient's physiological parameters in a medical environment is an important element of patient diagnosis and treatment. Within a modern medical facility, such as a hospital, such monitoring is relatively easy to perform. The environment is controlled. The staff, including physicians, nurses, physician assistants and technicians, is qualified. Such facilities have equipment resources for enabling the monitoring of one or more patients for a variety of physiological parameters.

Unfortunately the advantages of a hospital environment with its resources and personnel do not exist at many trauma sites, such as those at accident scenes or at battlefield sites. First responders to an accident scene generally include an emergency medical technician (EMT). The EMT assesses the patient and, in conjunction with advice from medical personnel established by radio contact, initiates treatment. Typically the EMT stays with the patient during transport to a medical facility. The EMT can transfer his or her observations to personnel at the facility by interview and/or by written record.

An entirely different situation exists on a battlefield. On a battlefield a medic is attached to a particular unit. The medic treats a patient. When the medic completes treatment at the battlefield site, the patient is transported to another facility. However, the medic stays behind to attend to other patients. The medic's initial treatment protocol will be based on certain readings taken at the site. Then there are procedures for identifying the actions that were taken at the site. For example, if a sedative is administered, the medic may pin the syringe to the patient. Typically no interview occurs between the personnel at the medical facility, such as a field hospital, and the attending medic. Moreover, typically no information is recorded about the patient during initial treatment and transport to the field hospital.

Recently proposals have been made for personal monitoring systems for use in a battlefield environment. U.S. Pat. No. 6,198,394 (2001) to Jacobsen et al. discloses one such system for remote monitoring of personnel. This system utilizes a harness with a number of sensors to be worn continuously by a soldier. The sensors monitor a number of parameters including physiological variables. The harness carries a transmitting unit for transferring data to a central site.

U.S. Pat. No. 6,454,708 (2002) to Ferguson et al. discloses a portable remote patient tele-monitoring system using a memory card or a smart card. This system includes a multi-parameter sensor array applied to a patient's chest by means of a sensor band. The smart card or memory card stores measured data. Alternatively, a data logger carried by the patient receives the data. A base station receives the recorded information and transmits it to a remote monitoring site over a telecommunications link. The sensor band is disposable and has a limited life. For long-term monitoring, sensor bands may be replaced periodically.

U.S. patent Publication No. 2004/0147818 (2004) to Levy et al. discloses a portable system for monitoring and processing patient parameters in multiple operational modes. Specifically a data acquisition processor receives data from sensors on a patient and processes that data. The processed data is communicated to a docking station with a portable monitoring unit in one operational mode or to a network access point in a wireless network in another operational mode.

As will be apparent, each of these proposals requires the use of bulky equipment. The Jacobsen et al. patent requires a soldier to wear a harness to be worn at all times. First, such a requirement requires the soldier to carry extra weight and to take precautions to avoid damaging the equipment during normal use. It is not likely that such a harness would be an acceptable alternative for application to a trauma patient on a battlefield or at another trauma site. Such apparatus is bulky, so it would be difficult to inventory such harnesses for multiple patients. In addition, medical personnel would have the additional burden of placing the harness on a trauma patient under adverse circumstances.

Each of these systems depends upon the availability of sophisticated communications links, such as those available in a hospital environment. They are not always available at a trauma site or on the battlefield. The use of smart cards or memory cards as suggested in the Ferguson et al. patent present problems because such devices are prone to being lost at a trauma site or during patient transport to a hospital or other central site. Further, only the data measured at the trauma site is recorded.

Oftentimes it is desirable for a medic to obtain a patient's blood pressure at the trauma site. In accordance with a popular method, a medic inflates a blood pressure cuff and then slowly deflates the cuff while monitoring the radial artery with a stethoscope to obtain the systolic and diastolic pressure readings. These devices are bulky for field use. Moreover, they do not record data. Consequently, the medic must record the blood pressure manually, typically by preparing a written record.

Other approaches have been proposed for providing various functions related to monitoring pulse waveforms and the like. For example, U.S. Pat. No. 3,742,937 (1973) to Manuel et al. discloses a cardiac monitor for generating an alarm if a patient's heart rate exceeds a threshold. The monitor includes a pressure sensitive diaphragm for sensing the pulse wave transmitted from the heart. A mechanico-electrical transducer, in the form of a strain gauge or capacitive element converts the pulse into a digital signal.

U.S. Pat. No. 5,722,414 (1998) to Archibald et al. discloses a blood pressure monitoring system including a transducer, a side wall, a flexible diaphragm and a fluid coupling medium. This sensor is adapted to be strapped to the wrist and includes means, including an electric motor for properly positioning and maintaining pressure during the measurement.

U.S. Pat. No. 6,514,212 (2003) to Ide et al. discloses a hemadynamometer with an air bag that is wrapped about the wrist for obtaining oppression or ischemia of the radial artery. A pneumatic pump pressurizes the air bag until ischemia is realized. A constant exhaust valve then gradually exhausts the bag while a pressure sensor detects the pulse signals of the radial artery. These signals are converted to digital signals for analysis and for obtaining blood pressure.

U.S. patent Publication No. US 2004/0167414 (2004) to Tanabe et al. discloses pulse wave monitoring device for obtaining a physiological characteristic such as an arteriosclerosis index.

Each of these approaches also tends to be bulky and expensive. What is also needed is a patient monitoring system that is adapted for providing a blood pressure measurement at a trauma site. What is also needed is a patient monitoring system that enables a recorded blood pressure at a trauma site to be electronically recorded for transport with the patient to a hospital or other medical facility. What is also needed is a patient monitoring system in which the components required for obtaining blood pressure can be combined with components for providing other functions.

SUMMARY

Therefore it is an object of this invention to provide patient blood pressure measurement apparatus that is adapted for use in a variety of environments including battlefield environments.

Another object of this invention is to provide apparatus for measuring blood pressure upon the arrival of a first responder or medic at a site and recording that measurement for transport with the patient to a medical facility.

Yet another object of this invention is to provide patient monitoring apparatus that is easy to use and facilitates the measurement of blood pressure.

In accordance with one aspect of this invention, apparatus for recording a pulse waveform generated at a measurement site on a patient's body includes a rigid housing that can be brought into proximity to an artery at the measurement site. A pressure transducer mounts to one side of the housing for generating an electrical signal that is a function of pressure at an input to the pressure transducer. A passage is formed through the housing from the input of the pressure transducer to communicate with the interior of bladder mounted to the other side of the housing. The bladder forms a sealed, fluid-filled cavity at the passage. Consequently when the bladder is brought into contact with skin at the measurement site, the pressure transducer produces a representation of a wave-form signal including pressure changes due to changes in the blood pressure in the artery.

In accordance with another aspect of this invention a system for obtaining a measurement of a patient's blood pressure includes a sensing-recording device and a probe. The sensing-recording device attaches to the patient and includes a memory, at least one sensor for measuring a physiological parameter and a memory for storing time-stamped samples of the physiological parameter in said memory. The probe is adapted for being applied with an application pressure to a measurement site remote from the site of said sensing-recording device. The probe generates a signal representing a pulse wave form at the measurement site for storage in a probe memory as time-stamped samples of the signal. The probe generates a representation of the patient's blood pressure based upon the retrieved time-stamped samples from said memory in said sensing-recording device in the probe memory.

In accordance with still another aspect of this invention a sensing-recording device that provides to an output device a history of a medical parameter of a patient includes a housing, a power supply in the housing and circuitry for storing in a memory data that represents the medical parameter. A normally open switch includes a locking structure that is operable when the switch is closed energizing the circuitry thereby to block any attempt to disconnect the power supply from the circuitry.

BRIEF DESCRIPTION OF THE DRAWINGS

The various objects, advantages and novel features of this invention will be more fully apparent from a reading of the following detailed description in conjunction with the accompanying drawings in which like reference numerals refer to like parts, and in which:

FIG. 1 depicts monitoring apparatus in accordance with this invention;

FIG. 2 is a different perspective view of a sensing-recording device shown inFIG. 1;

FIGS. 3 and 4 are two views of the interior of the sensing-recording device shown inFIG. 2;

FIG. 5 is a block diagram of the circuitry associated with the sensing-recording device shown inFIGS. 1 through 4;

FIG. 6 is an exploded perspective view of a portion of the probe shown inFIG. 1;

FIG. 7 is a view of the interior of the portion of the probe shown inFIGS. 1 and 6;

FIG. 8 is a block diagram of the electronic circuitry of the probe ofFIGS. 1,6 and7;

FIG. 9 is a flow diagram that depicts the operation of the probe and interaction with a sensing-recording device;

FIG. 10 is a flow diagram of one blood measurement method that can be undertaken using the probe and sensing-recording device ofFIG. 1; and

FIG. 11 depicts a graphical display obtained when making a blood pressure measurement.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

InFIG. 1patient monitoring apparatus210 includes asensor button211 that includes the capability of sensing and recording data related to a medical parameter, hereinafter a “sensing-recording device” and aprobe212. A medic can carry multiple sensing-recording devices and attach one sensing-recording device211 to each patient. In the following discussion the term “medic” normally identifies military personnel; however, in conjunction with this invention the term includes both military personnel and civilian personnel, such as EMTs. Each medic will also have asingle probe212. Anindividual probe212 may be used in conjunction with multiple sensing-recording devices, such as the sensing-recording device211, for multiple patients.

Sensing-Recording device211

As particularly shown inFIGS. 1 through 4, the sensing-recording device211 includes a base unit orhousing213, a clip having atransverse portion214 and aclip arm215 spaced from and essentially parallel to thehousing213. Thehousing213 carries an on/offswitch216 and a portion of a communications link in the form of an IrDA (Infrared Data Association) transceiver located behindwindow217 inFIG. 1. Theclip arm215 andhousing213 provide a means for attaching the sensing-recording device211 to the patient. For purposes described later, the free end of theclip arm215 may include a tear-drop portion218 or other like element partially for patient comfort.

Both thehousing213 andarm215 include sensing elements. In the embodiment shown inFIG. 2 theclip arm215 carries a sensor, such as represented by a dermal phase meter (DPM)electrode assembly220. The clip arm may also include atemperature sensor226 andphotocell221 as shown inFIG. 5. These sensors connect through conductors embedded in theclip arm215 and link214 to circuitry in thehousing213. Thehousing213 may include other elements such as light emitting diodes (LED)222 (shown inFIG. 5) for generating light in the red and infrared bandwidths for being sensed by thephotocell221 for pulse oximetry as known in the art. When a sensing-recording device includes optical devices in theclip arm215, the tear-drop portion218 serves to reduce ambient energy from reaching these sensors. It will become apparent that other sensors could be substituted for each or all of these specific sensors or added thereto.

In use a medic will, upon arrival at a patient, attach one sensing-recording device211 to that patient. For example the sensing-recording device211 could be attached by sliding theclip arm215 into the patient's mouth and positioning thehousing213 on the patient's cheek.

FIG. 5 is a block diagram of the circuitry of the sensing-recording device211. As shown, theclip arm215 includes theDPM electrode assembly220 with aninner electrode223, an outerannular electrode224 and intermediateannular insulator225.

In this embodiment thetemperature sensing element226 is also included in theclip arm215. It is shown separately inFIG. 5, but can be incorporated as part of theDPM electrode assembly220.FIG. 5 also depicts thephotocell221.

Each of these sensors produces a signal that is transferred to acontroller230 located in thehousing213. In thisspecific embodiment amplifiers231 and232 convey amplified analog signals representing skin impedance and temperature to thecontroller230. Anamplifier233 and filter234 provide signals to thecontroller230 from thephotocell221 representing specific frequencies of the light emitted by theLEDs222.

When the on/offswitch216 closes there is a connection between abattery235 and a regulated power supply (REG P/S)236 for energizing thecontroller230 with aninternal clock237. Acontrol240 operates so thecontroller230 interacts with memory. In this specific embodiment the memory is partitioned intoBUTTON MEM1memory241 andBUTTON MEM2memory242. Other partitioning or even separate memories could also be used. As will become apparent, functionally the memory can be considered as having two partitions. Thecontroller230 also interacts with theIrDA transceiver243 that would be located behind thewindow217 inFIG. 1.

FIGS. 3 and 4 depict a view of a disposablesensing recording device211 and particularly the structure of an ON/OFF switch216 that is particularly adapted for use with this device.Switch216 is designed to be moved from an OFF or open position that corresponds to its storage position to an ON position thereby energizing the components within the sensing-recording device211. Once the sensing-recording device211 is energized, it is imperative that it continue to be energized until the patient arrives at a medical facility and all the data is downloaded from the sensing-recording device211.

As shown inFIGS. 3 and 4, the ON/OFF switch216 includes acover316 with a diametrically extendingrib317 that facilitates manual rotation of thecover316 and its underlying components. Thecover316 attaches to ashaft318 mounted for a rotation in thehousing213 between a manually-open position and a closed position. Referring particularly toFIG. 4, theshaft318 carries afirst spring320 with a singleradial arm321 keyed to theshaft318. Amachine screw322 attaches the foregoing and other components to theshaft318. In an OFF, or manually-open position thearm321 lies on anarcuate segment323 abutting apost324. There is agap325 in thearcuate segment323 that defines an ON or closed position. Thus when thecover316 is rotated, it rotates from the OFF position shown inFIG. 4 to the ON position, theradial arm321 locks into thegap325 and prevents any further rotation of thecover316.

As the cover rotates from the OFF position to the ON position, aspring contact326 keyed to theshaft318 also rotates. It has two diametrically opposed radially extending electronicallyinterconnected arms327 and328. In an OFF position thearms327 and328 contact insulating material. When the switch reaches the ON position thespring contacts327 and328 overlieconductive pads331 and332, respectively. As shown inFIG. 1,rib317 is at right angles toindicia333 on the surface of thehousing213. When thecover316 rotates to the ON position, therib317 aligns with theindicia333 thereby to provide a positive indication that the sensor-recording device211 has been energized. Moreover, as will be apparent, once theswitch216 is turned on, it can not be turned off. This assures that the sensing-recording device211 remains active for the life of thebatteries235 inFIG. 5.

Thus after sensing-recording device211 has been attached to a patient, the medic rotates the on/offswitch216 to energize the controller. As described in more detail later, communications are then established between theprobe212 and the sensing-recording device211. When this occurs, acontrol240 begins to sample the outputs of the various sensors from theclip arm215 and activates anLED driver244 to begin the measurement sampling sequence. Thecontrol240 transfers each sample into theBUTTON MEM1memory241. Typically theBUTTON MEM1memory241 will have a capacity to store samples for 12 hours or so and may also act as a FIFO stack. In a preferred embodiment no sampled data is applied to theBUTTON MEM2memory242.

In response to other communications thecontrol240 decodes information from anIrDA transceiver243 for being loaded intoBUTTON MEM2memory242 and for transferring data from theBUTTON MEM1memory241 to theprobe212. Thecontroller230 also includes circuitry (not shown, but known in the art) for converting signals from the various sensors in theclip arm215 into digital formats for recording in theBUTTON MEM1memory241. Each sample is time-stamped with information from theclock237. As described later, the time in theclock237 is established by communications between theprobe212 and the sensing-recording device211.

Thecontroller230 also may include astorage register245 for storing a permanent unique serial number. As described later, this serial number is useful in assuring that data about one patient is not inadvertently transferred to the sensing-recording device211 for another patient.

Probe212

Now referring toFIGS. 1,6 and7,probe212 has ahousing250 that extends betweenopposite end portions251 and252. Theend portion251 carries aDPM electrode assembly256. ThisDPM electrode assembly256 may also include a temperature sensor, not shown.

Thehousing250 also carries adigital display260 proximate theother end portion252 as shown inFIG. 1. In this specific embodiment, afirst keypad261 has four scroll buttons for allowing the medic to move information on thedisplay260 transversely or parallel to the probe axis. Anotherkeypad262 may include an on/offbutton263 and an “ENTER”button264. Other structures may be substituted.

Referring toFIG. 1, theprobe212 includes an IrDA transceiver, not shown inFIG. 1, but located in the end of ahousing250 behind a window at theend portion252.

FIGS. 1,6 and7 disclose aprobe212 that carries abladder assembly338 and forms achamber339 in which the various probe components are carried that can provide signals representing the pulse wave-form of the radial artery or of some other measurement site. As specifically shown inFIG. 6, the exterior surface of thehousing250 includes an integrally formed, raisedplatform340. Aninsert341 has anaperture342 that provides a fluid passage. This insert terminates in a stub on the interior of thehousing250 which is not shown. Referring toFIG. 7,tubing343 attaches to the stub and to apressure transducer344.FIG. 7 depicts a representation of aconnector assembly345 that interfaces thepressure transducer344 to aprobe controller278.

FIGS. 6 and 7 also depict a controlledleak element346 that extends through theplatform340. A controlled leak element, such as controlledleak element346, is well known in the art as a means for slowly achieving equal pressure on both sides of the controlledleak element346. In this particular embodiment a disk includes a plurality of chemically-milled apertures.

In addition thehousing347 as shown inFIG. 7 may include a second controlledleak element346 that interfaces between the pressure on thechamber339 and ambient atmosphere.

Referring again toFIG. 6, thebladder338 is completed by means of amembrane350 formed of a non-allergenic soft, compliant, thin, elastomer material, such as a silicone-based material. Aperipheral flange351 adheres to thehousing250 adjacent the periphery of theplatform340. Aconcave portion352 integral with theflange351 produces a closedend channel chamber353 which has fluid communications with the pressure transducer through theaperture342 andtubing343 inFIG. 7.

When a medic wishes to take a measurement, theprobe212 is placed over a measurement site, such as the radial artery and a force is applied typically by squeezing theprobe212 against the patient's arm with thebladder338 positioned over the measurement site. With appropriate pressure, pressure changes are conveyed through the thin material of themembrane350, the fluid in thecavity353 and then through theaperture342 andtubing343 to the input of thepressure transducer344.

The value of theoutput signal344 represents the instantaneous pressure within thebladder338. This instantaneous pressure has two components. A first component is the pressure due to the force with which the probe is applied to the patient's arm. The second is due to the pressure within the artery being measured. The first component will vary slowly in comparison to the second component over time.

FIG. 8 depicts one embodiment of control circuit for providing the various probe functions. Anamplifier270 provides signals from theDPM electrode assembly256 to aprobe interface271. Theprobe interface271 also interfaces signals from a temperatureresponsive element272 provided by anamplifier273 and includes acurrent source274 for energizing abridge275 so anamplifier276 produces a force measurement signal. Thebridge275 can be collocated with thetemperature sensor272 andDPM electrode assembly256 as known in the art.

Basically theprobe interface271 converts signals from the various sensors into a digital format for transmission across apath277 to a computer-drivenprobe controller278. Theprobe controller278 also interfaces with the first andsecond keypads261 and262, thedisplay260 and anIrDA transceiver279 that is located behind a window at theend252 of theprobe212.

Theprobe controller278 includes a program controlled central processor represented as aprogram control280. Theprobe controller278 also includes aclock281 that can be synchronized to any real time through interaction between thedisplay260 and thekeypads261 and262. Amedical data memory282 stores any information provided by medicaldata application programs283, such as an OMAS program for converting signals from the various sensors attached to the probe interface into an Oral Mucositis Assessment Scale (OMAS) value or, for implementing one embodiment of this invention, a blood pressure measurement program. Themedical application programs283 produce the data in themedical data memory282 along with time stamps based upon information from theclock281. All these operations occur in response to aprobe operation program284.

Theprobe controller278 additionally includes an “in use”serial number register285 for use as described hereinafter.

Still referring toFIG. 8 and as previously described the output signal from thepressure transducer344 shown inFIGS. 7 and 8 represents the instantaneous total pressure applied at the input of atransducer344. This output signal is defined as a raw data signal and it is conveyed to theprobe controller278. Aband pass filter354 also receives the raw data signal. The pass band for thefilter354 is in the range of 0.1 to 10 Hz to correspond to typical heart rates. Theprobe controller278 also receives that signal as a filtered data signal.

Operation

Theprobe operation program284 as shown inFIGS. 9 and 10 defines a series of tasks including proposed actions to be displayed through instructions on thedisplay260 and reactions in response to data received either from theprobe interface271, theIrDA transceiver279 or thekeypads261 and262. A medic might be able to initiate the use of theprobe212 in a variety of ways. For example, the medic might manipulate the display using thekeypad261 inFIG. 1 until a “New Patient” procedure is displayed and then activate theENTER key263.FIG. 9 shows another approach in which the medic attaches a sensor-recording button211 to a patient, turns thedevice211 on and then brings theprobe212 into proximity to establish communications as indicated bystep290. If communications are not established after a predetermined period of time,step291 transfers control to step292 thereby to display an error message and to await a next action.

Assuming communications are established, control transfers to step293 whereupon the probe reads the data in theserial number register245 and the “in use”serial number register285. If the medic is returning to the same patient, the serial numbers match. So, control passes fromstep294 toFIG. 10. If the medic has not been working with a patient previously, the numbers are not the same and the patient is new. Step294 diverts control to step295 that clears the data in both themedical data memory282 and “in use”serial number register285.

Step296 then enables a first synchronization procedure. Assuming that the medic has energized the sensing-recording device211 by activating the on/offswitch216,step297 synchronizes theclock237 in the sensing-recording device211 shown inFIG. 5 to theclock281 in the probe controller ofFIG. 8. Specifically, theclock237 will have begun operation at some random time when the on/off switch has been activated. Step297 allows the synchronization to occur and theclock237 then to be updated. Typically theclock237 will then run as accurately or nearly as accurately as theclock281.

If the synchronization ofstep297 can not be completed successfully, step300 transfers control to step292 to display an error message and potentially provide information with respect to recovering from the error.

Once the clock synchronization has occurred, the program operation control usesstep302 to communicate through theIrDA transceivers243 and279 inFIGS. 5 and 8 to enable the sensing-recording device211 to record readings in theBUTTON MEM1memory241. Step303 represents a process during which a medic can use theprobe212 to take additional readings independently using one or more of the medicaldata application programs283 with results being recorded in the probemedical data memory282. These readings may also be under control of the program with appropriate displays specifying specific tasks to be taken.

When the medic has completed actions instep303,step304 initiates a process by which the medic retrieves information from theBUTTON MEM1memory241 that contains the time stamped data relating to the monitoring operation by the sensing-recording device211. When all the data has been retrieved, step305 processes the information in the probemedical data memory282, including the information from theBUTTON MEM1memory241, to produce results as feedback to the medic according to medicaldata application programs283. For example, one display might be a graphical representation of OMAS values over a period of time. During this interval, the sensing-recording device211 continues to add data to theBUTTON MEM1memory241.

Whenstep305 completes its operations, step306 transfers selected data from themedical data memory282 to theBUTTON MEM2memory242. Thus theBUTTON MEM2memory242 contains all the results of the readings taken by the medic at the battlefield site and the results of any data that was contained in theBUTTON MEM1memory241 that was processed instep305. Whenstep306 is completed, control transfers to step400 inFIG. 10 to await the initiation of a new task.

FIG. 10 represents the process by which various tasks are initiated. As disclosed theprobe controller278 remains in a wait state until a task request is received instep400. One of those tasks could be initiated by the medic through thekeypads261 and262. When a task request is received,step401 identifies the task. For tasks other than blood pressure, step401 branches to step402 for performing the requested task. When that is complete, control returns to step400 to await the initiation of a next task.

When the medic wishes to take blood pressure, step401 transfers to step403 which represents the application of theprobe212 with thebladder338 over the radial artery or other measurement site. As this occursstep404 provides an indication on display of the value of the pressure.

More specifically,step405 represents the sampling of the raw data from thepressure transducer344 and the filtered data from theband pass filter354. For each sample, the raw data and the filter data are stored in corresponding data sets with time stamps. In addition the processor may use a moving average over some time of the raw data to generate the signal representing the pressure being applied.

As shown inFIG. 11 this average pressure value can be displayed as abar graph412 or by some other graphical representation. Thedisplay260 will also provide two lines413 and414 bounding the acceptable range of force applied by the medic. Therefore the medic merely needs to observe this display to assure the optimal pressure is applied. Theboundaries413 and414 may be fixed. Alternatively if a quality analysis is performed on the filtered data, the boundaries may be movable as a function of such analysis. This feedback is helpful in assuring appropriate pressures are applied by the medic.

After the information has been obtained and recorded instep406,step407 represents a process by which the corresponding data sets are read from the BUT1MEM memory241, particularly the data representing the pulse oximetry obtained by the sensing-recording device211. Step410 then correlates the measurement times in the two data sets through a best fit or other analysis. The difference between the timing represents the times required for a particular pulse to travel from the heart to the patient's cheek and the heart to the radial artery. As known, this time of flight data is useful in deriving a blood pressure reading which then can be displayed bystep411. The data can also be recorded in the BUT2MEM memory242. In this way the blood pressure is recorded and travels with the patient to the next medical facility. Alternatively the blood pressure measurement process ofFIG. 10 could merely store the wave forms obtained during the blood measurement in the sensing-recording device211.

Thus, when the patient is transported, the sensing-recording device211 contains data in theBUTTON MEM2memory242 that identifies his condition when the medic attended the patient. TheBUTTON MEM1memory241 contains the time stamped raw data that continues to be obtained from the various sensors in the sensing-recording device211.

When the patient reaches a medical facility, it is a simple matter for a properly equipped data processing system, such as a laptop computer with an IrDA port, to communicate with thecontroller230 in the sensing-recording device211 and download all the data from both theBUTTON MEM1memory241 and theBUTTON MEM2memory242. This data can be further processed in accordance with various application programs to provide further diagnostic information. Unlike the prior art, however, this information provides a continuum of patient data from the time first synchronization procedure is initiated until the time the data is downloaded from the patient.

As will now be apparent, apparatus constructed in accordance with this invention and based upon the specific embodiment shown inFIGS. 1 through 10 provides patient monitoring apparatus that is adapted for use in a variety of environments including battlefield environments. This patient monitoring apparatus is easy to use and facilitates the measurement of diverse physiological parameters. Moreover, the apparatus enables the monitoring of these parameters from the arrival of a medic or a first responder at the patient to the arrival of the patient at a medical facility.

It will also be apparent that this invention has been described with respect to a specific embodiment with particular organization of components and controls. A number of variations can be made by those of ordinary skill in the art without departing from this invention. For example, the sensing-recording device211 is shown with a structure particularly suitable for disposing the sensing-recordingdevice housing213 on a patient's cheek with theclip arm215 within the mouth. Other form factors could be utilized that would adapt the function of the sensing-recording device211 for attachment to other parts of the body, such as an earlobe, as might be dictated by a particular set of physiological parameters being measured. Theprobe212 has been shown as a single device with particular form factor and layout of controls. Each of those could be modified to adapt the probe to different ergonomic or other conditions.

SimilarlyFIGS. 5 and 8 depict particular embodiments of the electronics carried within the sensing-recordingdevice housing213 and probehousing250. Different sensors could be substituted for any of the specifically disclosed sensors. Different memory organizations could be utilized. Communications using mechanisms other than IrDA transceivers could be used. The organization of a control, such as thecontrol240 inFIG. 5 and theprogram control280 inFIG. 8 could be changed.FIG. 8 depictsprobe interface271 and aprobe controller278. In other embodiments the functions of these two elements could be combined in a single unit. Consequently it is the intent to claim this invention to cover this particular embodiment and any equivalent embodiments that may be developed.

Claims (8)

1. A system for obtaining a measurement of a patient's blood pressure comprising:

A) sensing-recording means for attachment to the patient including a memory, sensing means for measuring a predetermined physiological parameter, and means for storing time-stamped samples of the predetermined physiological parameter in said memory as a first data set, and

B) a probe for being applied with an application pressure to a measurement site remote from the site of said sensing-recording means, said probe including:

i) means for generating a signal representing a pulse wave form at the measurement site,

ii) a probe memory,

iii) means for storing times-stamped samples of the signal in said probe memory as a second data set,

iv) means for retrieving the time-stamped samples from said memory in said sensing-recording means,

v) means for correlating the measurement times for the first and second data sets,

vi) means for generating a representation of the patient's blood pressure based upon the information in said correlated, time-stamped data sets.

2. A system as recited inclaim 1 wherein said probe comprises:

i) rigid housing means for being brought into proximity to an artery at the measurement site,

ii) pressure transducer means mounted to one side of said housing means for generating an electrical signal that is a function of pressure at an input thereto,

iii) flexible membrane means mounted to the other side of said housing for forming a sealed, fluid-filled cavity about said passage means at said housing means, and

iv) passage means formed through said housing means for connection to said pressure transducer means input whereby when said flexible membrane means is brought into contact with the skin at the measurement site, said pressure transducer means produces a representation of a wave-form signal corresponding to the pressure changes at the measurement site.

3. A system as recited inclaim 2 wherein said flexible membrane means includes a thin, flexible elastomer formed into a closed-end channel and a peripheral flange attachment to said other side of said rigid housing means.

4. A system as recited inclaim 3 wherein said rigid housing means forms a chamber for receiving said pressure transducer means, said apparatus including a controlled leak means for long-term pressure equalization between said cavity and said chamber.

5. A system as recited inclaim 1 wherein said sensing means in said sensing-recording means includes means for measuring pulse oximetry whereby the first data set stored in said sensing-recording means memory represents blood oxygenation.

6. A system as recited inclaim 5 wherein during a measurement said probe is applied to the measurement site with an application pressure and said pressure transducer means generates a composite signal representing the application pressure and the pressure at the measurement site, said probe including processing means for storing data representing the pulse wave form produced at the measurement site as the second data set.

7. A system as recited inclaim 6 wherein said processing means includes band pass filter means for generating a filtered data signal in response to the composite signal whereby said processing means responds to both the composite and filtered data signals.

8. A system as recited inclaim 7 wherein processing means includes means generating a graphical display of the application pressure in response to the composite data.

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